Next generation ultra-long haul optical networks will include hybrid data rate dense wavelength division multiplexing (DWDM) optical mesh networks that support, for example, both 10-Gb/s and 40-Gb/s signal transmission. In such mesh networks 10-Gb/s and 40-Gb/s signals are transmitted in the same transmission fiber and can originate and terminate anywhere in the network.
To make these hybrid data rate mesh networks practicable and cost-effective, a scalable dispersion management scheme or dispersion map is desirable. This requires pre-, post- and in-line dispersion compensation to be independent of both transmission distance and data rate. Such requirements pose significant design challenges since different dispersion management requirements arise for different data rates. For example, optimal performance for 10-Gb/s signal transmission usually requires non-zero residual dispersion in transmission spans, links and paths, while 40-Gb/s signal transmission usually requires zero residual dispersion.
Prior art solutions have proposed dispersion maps for point-to-point single data rate optical transmission systems. It has been shown that for 40-Gb/s systems employing a singly periodic dispersion map, the required pre- and post-dispersion compensation is dependent on transmission distance. Thus, if a singly periodic dispersion map is employed in a 40-Gb/s mesh network, tunable dispersion compensators (TDCs) with large tuning ranges are necessary in receivers or in transmitters to accommodate signals traveling different distances in the mesh network. This can significantly complicate the system control and increase the system cost.
One prior art solution to this problem proposes the use of a doubly periodic dispersion map, which fully compensates the residual dispersion in each link. This reduces the dependence of pre- and post-dispersion compensation on distance for 40-Gb/s transmissions. However, for 10-Gb/s transmission, which requires non-zero residual dispersion, doubly periodic dispersion maps with zero residual dispersion can lead to unacceptable inter-channel cross-phase modulation (XPM).
Prior art solutions for addressing inter-channel XPM have proposed demultiplexing WDM signals in each span of a transmission link to introduce variable delays to each channel of the WDM signal. These channel-based solutions, however, require large numbers of tunable delay devices to force destructive interference between all channels in every span of every link of a network. Such solutions are not cost effective, and are accordingly impractical.